AR# 44399: LogiCORE IP Spartan-6 FGPA Triple-Rate Serial Digital Interface (SDI) v1.0 - Why do the rx_t_ signals say that the identity is not necessarily the same as the data?

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Solution

The user can find more information on why the description says thisin the Bit Rate and Transport Format Detection section on page 38 of UG824. Thesesignals will detect the transport information, but to find the actual video payload information the user must read the VPID packet. On page 45 of UG824, the VPID is made available to the user on the rx_a_vpid port, and should be qualified by the rx_a_vpid_valid port.

It should also be noted thatfor SD-SDI and HD-SDI, the ST 352 payload ID packet is optional and thus it may not be present. However, for SD-SDI and HD-SDI the transport format and the video format are always the same; so, if the rx_a_vpid_valid output is not asserted, the user can use the transport format. It is only for dual link HD-SDI and 3G-SDI where the transport may differ from the video format and the ST 352 payload ID packet is mandatory for dual link HD-SDI and 3G-SDI, although some pieces of dual link HD-SDI equipment do not adhere to this. In these cases, there is no defined way to know what the video format is.

It is recommended thatusersrefer to the SMPTE specifications for more information.